CH A P T E R
10
Configuring Radio Resource
ManagementWireless Device Access
This chapter describes radio resource management (RRM) and explains how to configure it on the
controllers. It contains these sections:
•
Overview of Radio Resource Management, page 10-2
•
Overview of RF Groups, page 10-5
•
Configuring an RF Group, page 10-6
•
Viewing RF Group Status, page 10-8
•
Enabling Rogue Access Point Detection, page 10-11
•
Configuring RRM, page 10-15
•
Overriding RRM, page 10-26
•
Viewing Additional RRM Settings Using the CLI, page 10-32
•
Configuring CCX Radio Management Features, page 10-32
•
Configuring Pico Cell Mode, page 10-37
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Overview of Radio Resource Management
Overview of Radio Resource Management
The radio resource management (RRM) software embedded in the controller acts as a built-in RF
engineer to consistently provide real-time RF management of your wireless network. RRM enables
controllers to continually monitor their associated lightweight access points for the following
information:
•
Traffic load—The total bandwidth used for transmitting and receiving traffic. It enables wireless
LAN managers to track and plan network growth ahead of client demand.
•
Interference—The amount of traffic coming from other 802.11 sources.
•
Noise—The amount of non-802.11 traffic that is interfering with the currently assigned channel.
•
Coverage—The received signal strength (RSSI) and signal-to-noise ratio (SNR) for all connected
clients.
•
Other access points—The number of nearby access points.
Using this information, RRM can periodically reconfigure the 802.11 RF network for best efficiency. To
do this, RRM performs these functions:
•
Radio resource monitoring
•
Dynamic channel assignment
•
Dynamic transmit power control
•
Coverage hole detection and correction
•
Client and network load balancing
Radio Resource Monitoring
RRM automatically detects and configures new controllers and lightweight access points as they are
added to the network. It then automatically adjusts associated and nearby lightweight access points to
optimize coverage and capacity.
Lightweight access points can simultaneously scan all valid 802.11a/b/g channels for the country of
operation as well as for channels available in other locations. The access point goes “off-channel” for a
period not greater than 60 ms to monitor these channels for noise and interference. Packets collected
during this time are analyzed to detect rogue access points, rogue clients, ad-hoc clients, and interfering
access points.
Note
If packets have been in the voice queue in the last 100 ms, the access point does not go off-channel.
By default, each access point spends only 0.2 percent of its time off-channel. This activity is distributed
across all access points so that adjacent access points are not scanning at the same time, which could
adversely affect wireless LAN performance. In this way, administrators gain the perspective of every
access point, thereby increasing network visibility.
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Dynamic Channel Assignment
Two adjacent access points on the same channel can cause either signal contention or signal collision.
In the case of a collision, data is simply not received by the access point. This functionality can become
a problem, for example, when someone reading e-mail in a café affects the performance of the access
point in a neighboring business. Even though these are completely separate networks, someone sending
traffic to the café on channel 1 can disrupt communication in an enterprise using the same channel.
Controllers address this problem by dynamically allocating access point channel assignments to avoid
conflict and to increase capacity and performance. Channels are “reused” to avoid wasting scarce RF
resources. In other words, channel 1 is allocated to a different access point far from the café, which is
more effective than not using channel 1 altogether.
The controller’s dynamic channel assignment capabilities are also useful in minimizing adjacent channel
interference between access points. For example, two overlapping channels in the 802.11b/g band, such
as 1 and 2, cannot both simultaneously use 11/54 Mbps. By effectively reassigning channels, the controller
keeps adjacent channels separated, thereby avoiding this problem.
The controller examines a variety of real-time RF characteristics to efficiently handle channel
assignments. These include:
•
Access point received energy—The received signal strength measured between each access point
and its nearby neighboring access points. Channels are optimized for the highest network capacity.
•
Noise—Noise can limit signal quality at the client and access point. An increase in noise reduces
the effective cell size and degrades user experience. By optimizing channels to avoid noise sources,
the controller can optimize coverage while maintaining system capacity. If a channel is unusable due
to excessive noise, that channel can be avoided.
•
802.11 Interference—Interference is any 802.11 traffic that is not part of your wireless LAN,
including rogue access points and neighboring wireless networks. Lightweight access points
constantly scan all channels looking for sources of interference. If the amount of 802.11 interference
exceeds a predefined configurable threshold (the default is 10 percent), the access point sends an
alert to the controller. Using the RRM algorithms, the controller may then dynamically rearrange
channel assignments to increase system performance in the presence of the interference. Such an
adjustment could result in adjacent lightweight access points being on the same channel, but this
setup is preferable to having the access points remain on a channel that is unusable due to an
interfering foreign access point.
In addition, if other wireless networks are present, the controller shifts the usage of channels to
complement the other networks. For example, if one network is on channel 6, an adjacent wireless
LAN is assigned to channel 1 or 11. This arrangement increases the capacity of the network by
limiting the sharing of frequencies. If a channel has virtually no capacity remaining, the controller
may choose to avoid this channel. In very dense deployments in which all non-overlapping channels
are occupied, the controller does its best, but you must consider RF density when setting
expectations.
•
Utilization—When utilization monitoring is enabled, capacity calculations can consider that some
access points are deployed in ways that carry more traffic than other access points (for example, a
lobby versus an engineering area). The controller can then assign channels to improve the access
point with the worst performance (and therefore utilization) reported.
•
Load—Load is taken into account when changing the channel structure to minimize the impact on
clients currently in the wireless LAN. This metric keeps track of every access point’s transmitted
and received packet counts to determine how busy the access points are. New clients avoid an
overloaded access point and associate to a new access point.
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Overview of Radio Resource Management
The controller combines this RF characteristic information with RRM algorithms to make system-wide
decisions. Conflicting demands are resolved using soft-decision metrics that guarantee the best choice
for minimizing network interference. The end result is optimal channel configuration in a
three-dimensional space, where access points on the floor above and below play a major factor in an
overall wireless LAN configuration.
Dynamic Transmit Power Control
The controller dynamically controls access point transmit power based on real-time wireless LAN
conditions. Normally, power can be kept low to gain extra capacity and reduce interference. The
controller attempts to balance access points such that they see their fourth strongest neighbor at an
optimal –65 dbm or better.
The transmit power control algorithm only reduces an access point’s power. However, the coverage hole
algorithm, explained below, can increase access point power, thereby filling a coverage hole. For
example, if a failed access point is detected, the coverage hole algorithm can automatically increase
power on surrounding access points to fill the gap created by the loss in coverage.
Note
See Step 4 on page 10-29 for an explanation of the transmit power levels.
Coverage Hole Detection and Correction
RRM’s coverage hole detection feature can alert you to the need for an additional (or relocated)
lightweight access point. If clients on a lightweight access point are detected at signal-to-noise ratio
(SNR) levels that are lower than the thresholds specified in the Auto RF configuration, the access point
sends a “coverage hole” alert to the controller. The alert indicates the existence of an area where clients
are continually experiencing poor signal coverage, without having a viable access point to which to
roam. The administrator can look up the historical record of access points to see if these alerts are
chronic, indicating the existence of a persistent coverage hole as opposed to an isolated problem.
Client and Network Load Balancing
RRM load-balances new clients across grouped lightweight access points reporting to each controller.
This function is particularly important when many clients converge in one spot (such as a conference
room or auditorium) because RRM can automatically force some subscribers to associate with nearby
access points, allowing higher throughput for all clients. The controller provides a centralized view of
client loads on all access points. This information can be used to influence where new clients attach to
the network or to direct existing clients to new access points to improve wireless LAN performance. The
result is an even distribution of capacity across an entire wireless network.
Note
Client load balancing works only for a single controller. It is not operate in a multi-controller
environment.
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Overview of RF Groups
RRM Benefits
RRM produces a network with optimal capacity, performance, and reliability while enabling you to
avoid the cost of laborious historical data interpretation and individual lightweight access point
reconfiguration. It also frees you from having to continually monitor the network for noise and
interference problems, which can be transient and difficult to troubleshoot. Finally, RRM ensures that
clients enjoy a seamless, trouble-free connection throughout the Cisco unified wireless network.
RRM uses separate monitoring and control for each deployed network: 802.11a and 802.11b/g. That is,
the RRM algorithms run separately for each radio type (802.11a and 802.11b/g). RRM uses both
measurements and algorithms. RRM measurements can be adjusted using the monitor intervals specified
in Table 10-1, but they cannot be disabled. RRM algorithms, on the other hand, are enabled
automatically but can be disabled by statically configuring channel and power assignment. The RRM
algorithms run at a specified updated interval, which is 600 seconds by default.
Note
RRM measurements are postponed on a per access point basis where traffic remains in the platinum QoS
queue, if there was voice traffic in the last 100 ms.
Overview of RF Groups
An RF group, also known as an RF domain, is a cluster of controllers that coordinates its RRM
calculations on a per 802.11-network basis. An RF group exists for each 802.11 network type. Clustering
controllers into RF groups enables the RRM algorithms to scale beyond a single controller.
Lightweight access points periodically send out neighbor messages over the air. The RRM algorithms
use a shared secret that is configured on the controller and sent to each access point. Access points
sharing the same secret are able to validate messages from each other. When access points on different
controllers hear validated neighbor messages at a signal strength of –80 dBm or stronger, the controllers
dynamically form an RF group.
Note
RF groups and mobility groups are similar in that they both define clusters of controllers, but they are
different in terms of their use. These two concepts are often confused because the mobility group name
and RF group name are configured to be the same in the Startup Wizard. Most of the time, all of the
controllers in an RF group are also in the same mobility group and vice versa. However, an RF group
facilitates scalable, system-wide dynamic RF management while a mobility group facilitates scalable,
system-wide mobility and controller redundancy. Refer to Chapter 11 for more information on mobility
groups.
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Configuring an RF Group
RF Group Leader
The members of an RF group elect an RF group leader to maintain a “master” power and channel scheme
for the group. The RF group leader is dynamically chosen and cannot be selected by the user. In addition,
the RF group leader can change at any time, depending on the RRM algorithm calculations.
The RF group leader analyzes real-time radio data collected by the system and calculates the master
power and channel plan. The RRM algorithms try to optimize around a signal strength of –65 dBm
between all access points and to avoid 802.11 co-channel interference and contention as well as
non-802.11 interference. The RRM algorithms employ dampening calculations to minimize
system-wide dynamic changes. The end result is dynamically calculated optimal power and channel
planning that is responsive to an always changing RF environment.
The RRM algorithms run at a specified updated interval, which is 600 seconds by default. Between
update intervals, the RF group leader sends keep-alive messages to each of the RF group members and
collects real-time RF data.
Note
Several monitoring intervals are also available. See Table 10-1 for details.
RF Group Name
A controller is configured with an RF group name, which is sent to all access points joined to the
controller and used by the access points as the shared secret for generating the hashed MIC in the
neighbor messages. To create an RF group, you simply configure all of the controllers to be included in
the group with the same RF group name. You can include up to 20 controllers and 1000 access points in
an RF group.
If there is any possibility that an access point joined to a controller may hear RF transmissions from an
access point on a different controller, the controllers should be configured with the same RF group name.
If RF transmissions between access points can be heard, then system-wide RRM is recommended to
avoid 802.11 interference and contention as much as possible.
Configuring an RF Group
This section provides instructions for configuring RF groups through either the GUI or the CLI.
Note
The RF group name is generally set at deployment time through the Startup Wizard. However, you can
change it as necessary.
Note
When the multiple-country feature is being used, all controllers intended to join the same RF group must
be configured with the same set of countries, configured in the same order.
Note
You can also configure RF groups using the Cisco Wireless Control System (WCS). Refer to the Cisco
Wireless Control System Configuration Guide for instructions.
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Using the GUI to Configure an RF Group
Follow these steps to create an RF group using the GUI.
Step 1
Click Controller > General to access the General page (see Figure 10-1).
Figure 10-1
General Page
Step 2
Enter a name for the RF group in the RF-Network Name field. The name can contain up to 19 ASCII
characters.
Step 3
Click Apply to commit your changes.
Step 4
Click Save Configuration to save your changes.
Step 5
Repeat this procedure for each controller that you want to include in the RF group.
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Viewing RF Group Status
Using the CLI to Configure RF Groups
Follow these steps to configure an RF group using the CLI.
Step 1
Enter config network rf-network-name name to create an RF group.
Note
Enter up to 19 ASCII characters for the group name.
Step 2
Enter show network to view the RF group.
Step 3
Enter save config to save your settings.
Step 4
Repeat this procedure for each controller that you want to include in the RF group.
Viewing RF Group Status
This section provides instructions for viewing the status of the RF group through either the GUI or the
CLI.
Note
You can also view the status of RF groups using the Cisco Wireless Control System (WCS). Refer to the
Cisco Wireless Control System Configuration Guide for instructions.
Using the GUI to View RF Group Status
Follow these steps to view the status of the RF group using the GUI.
Step 1
Click Wireless > 802.11a or 802.11b/g > RRM > Auto RF to access the 802.11a (or 802.11b/g) Global
Parameters > Auto RF page (see Figure 10-2).
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Figure 10-2
802.11b/g Global Parameters > Auto RF Page
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The top of this page shows the details of the RF group, specifically how often the group information is
updated (600 seconds by default), the MAC address of the RF group leader, whether this particular
controller is the group leader, the last time the group information was updated, and the MAC addresses
of all group members.
Note
Step 2
Automatic RF grouping, which is set through the Group Mode check box, is enabled by default.
See Table 10-1 for more information on this parameter.
If desired, repeat this procedure for the network type you did not select (802.11a or 802.11b/g).
Using the CLI to View RF Group Status
Follow these steps to view the status of the RF group using the CLI.
Step 1
Enter show advanced 802.11a group to see which controller is the RF group leader for the 802.11a RF
network. Information similar to the following appears:
Radio RF Grouping
802.11a Group Mode............................. AUTO
802.11a Group Update Interval.................. 600 seconds
802.11a Group Leader........................... 00:16:9d:ca:d9:60
802.11a Group Member........................... 00:16:9d:ca:d9:60
802.11a Last Run............................ 594 seconds ago
This text shows the details of the RF group, specifically whether automatic RF grouping is enabled for
this controller, how often the group information is updated (600 seconds by default), the MAC address
of the RF group leader, the MAC address of this particular controller, and the last time the group
information was updated.
Note
Step 2
If the MAC addresses of the group leader and the group member are identical, this controller is
currently the group leader.
Enter show advanced 802.11b group to see which controller is the RF group leader for the 802.11b/g
RF network.
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Enabling Rogue Access Point Detection
Enabling Rogue Access Point Detection
Upon configuring the RF group settings on the controllers, you need to configure the access points
connected to the controllers to detect rogue access points. The access points will then check the beacon/
probe-response frames in neighboring access point messages to see if they contain an authentication
information element (IE) that matches that of the RF group. If the check is successful, the frames are
authenticated. Otherwise, the authorized access point reports the neighboring access point as a rogue,
records its BSSID in a rogue table, and sends the table to the controller.
LWAPP access points in local or monitor mode will automatically detect nearby rogue access points
based on the MAC address of the rogue access points. However, LWAPP access points cannot detect
rogue access points if the rogue access points contain the MAC address of a valid LWAPP access point.
If you configure access point authentication with management frame protection (MFP) disabled,
neighbor access points are authenticated, preventing the rogue access point from using the MAC address
of a valid LWAPP access point. If MFP is enabled, access point authentication of a neighbor cannot read
the encrypted management frames for the rogue access point verification.
The access points check the beacon or probe response frames in neighboring access point messages to
see if they contain an authentication information element (IE) that matches that of the RF group. If the
check is successful, the frames are authenticated. Otherwise, the authorized access point reports the
neighboring access point as a rogue, records its BSSID in a rogue table, and sends the table to the
controller.
Using the GUI to Enable Rogue Access Point Detection
Follow these steps to enable rogue access point detection using the GUI.
Step 1
Make sure that each controller in the RF group has been configured with the same RF group name.
Note
Step 2
The name is used to verify the authentication IE in all beacon frames. If the controllers have
different names, false alarms will occur.
Click Wireless to access the All APs page (see Figure 10-3).
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Figure 10-3
Step 3
All APs Page
Click the name of an access point to access the All APs > Details page (see Figure 10-4).
Figure 10-4
All APs > Details Page
Step 4
Choose either local or monitor from the AP Mode drop-down box and click Apply to commit your
changes.
Step 5
Click Save Configuration to save your changes.
Step 6
Repeat Step 2 through Step 5 for every access point connected to the controller.
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Step 7
Click Security > Wireless Protection Policies > AP Authentication/MFP to access the AP
Authentication Policy page (see Figure 10-5).
Figure 10-5
AP Authentication Policy Page
The name of the RF group to which this controller belongs appears at the top of the page.
Step 8
Choose AP Authentication from the Protection Type drop-down box to enable rogue access point
detection.
Step 9
Enter a number in the Alarm Trigger Threshold edit box to specify when a rogue access point alarm is
generated. An alarm occurs when the threshold value (which specifies the number of access point frames
with an invalid authentication IE) is met or exceeded within the detection period.
Note
The valid threshold range is from1 to 255, and the default threshold value is 1. To avoid false
alarms, you may want to set the threshold to a higher value.
Step 10
Click Apply to commit your changes.
Step 11
Click Save Configuration to save your changes.
Step 12
Repeat this procedure on every controller in the RF group.
Note
If rogue access point detection is not enabled on every controller in the RF group, the access
points on the controllers with this feature disabled are reported as rogues.
Using the CLI to Enable Rogue Access Point Detection
Follow these steps to enable rogue access point detection using the CLI.
Step 1
Make sure that each controller in the RF group has been configured with the same RF group name.
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Note
The name is used to verify the authentication IE in all beacon frames. If the controllers have
different names, false alarms will occur.
Step 2
Enter config ap mode local Cisco_AP or config ap mode monitor Cisco_AP to configure this particular
access point for local (normal) mode or monitor (listen-only) mode.
Step 3
Enter save config to save your settings.
Step 4
Repeat Step 2 and Step 3 for every access point connected to the controller.
Step 5
Enter config wps ap-authentication to enable rogue access point detection.
Step 6
Enter config wps ap-authentication threshold to specify when a rogue access point alarm is generated.
An alarm occurs when the threshold value (which specifies the number of access point frames with an
invalid authentication IE) is met or exceeded within the detection period.
Note
The valid threshold range is from1 to 255, and the default threshold value is 1. To avoid false
alarms, you may want to set the threshold to a higher value.
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Configuring RRM
Step 7
Enter save config to save your settings.
Step 8
Repeat Step 5 through Step 7 on every controller in the RF group.
Note
If rogue access point detection is not enabled on every controller in the RF group, the access
points on the controllers with this feature disabled are reported as rogues.
Configuring RRM
The controller’s preconfigured RRM settings are optimized for most deployments. However, you can
modify the controller’s RRM configuration parameters at any time through either the GUI or the CLI.
Note
The RRM parameters should be set to the same values on every controller in an RF group. If the RRM
parameters are not identical for all RF group members, varying results can occur if the group leader
changes (for example, if the current group leader goes offline and a new leader is chosen).
Using the GUI to Configure RRM
Follow these steps to configure RRM parameters using the GUI.
Step 1
Click Wireless > 802.11a or 802.11b/g > RRM > Auto RF to access the 802.11a (or 802.11b/g) Global
Parameters > Auto RF page.
Note
Click Set to Factory Default at the bottom of the page if you want to return all of the controller’s
RRM parameters to their factory default values.
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Step 2
Table 10-1 lists and describes the configurable RRM parameters. Follow the instructions in the table to
make any desired changes.
Table 10-1
RRM Parameters
Parameter
Description
RF Grouping Algorithm
Group Mode
Determines whether the controller participates in an RF group.
Options: Enabled or Disabled
Default: Enabled
Group Mode Description
Enabled
The controller automatically forms an RF group with
other controllers. The group dynamically elects a leader
to optimize RRM parameter settings for the group.
Disabled
The controller does not participate in automatic RF
grouping. Rather, it optimizes the access points
connected directly to it.
Note
Cisco recommends that controllers participate in automatic RF
grouping. However, you can disable this feature if necessary by
unchecking the check box. Note also, however, that you
override RRM settings without disabling automatic RF group
participation. See the “Overriding RRM” section on page 10-26
for instructions.
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Table 10-1
RRM Parameters (continued)
Parameter
Description
Dynamic Channel Assignment Algorithm
Channel Assignment
Method
The controller’s dynamic channel assignment mode.
Options: Automatic, On Demand, or Off
Default: Automatic
Channel
Assignment
Method
Automatic
Description
Causes the controller to periodically evaluate and, if
necessary, update the channel assignment for all joined
access points.
On Demand Causes the controller to periodically evaluate the channel
assignment for all joined access points. However, the
controller reassigns channels, if necessary, only when
you click Invoke Channel Update Now.
Note
Off
Note
Interval
The controller does not evaluate and update the
channel immediately after you click Invoke
Channel Update Now. It waits for the next
600-second interval. This value is not
configurable.
Prevents the controller from evaluating and, if necessary,
updating the channel assignment for joined access
points.
For optimal performance, Cisco recommends that you use the
Automatic setting. Refer to the “Disabling Dynamic Channel
and Power Assignment Globally for a Controller” section on
page 10-31 for instructions if you ever need to disable the
controller’s dynamic settings.
How often the DCA algorithm has been configured to run.
Range: 0 (10 minutes) and 1, 2, 3, 4, 6, 8, 12, and 24 hours
Default: 0
AnchorTime
The time of day when the DCA algorithm has been configured to start.
Range: 0 to 23 (12:00 a.m. to 11:00 p.m.)
Avoid Foreign AP
Interference
Causes the controller’s RRM algorithms to consider 802.11 traffic from
foreign access points (those not included in your wireless network)
when assigning channels to lightweight access points. For example,
RRM may adjust the channel assignment to have access points avoid
channels close to foreign access points.
Options: Enabled or Disabled
Default: Enabled
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Table 10-1
RRM Parameters (continued)
Parameter
Description
Avoid Cisco AP Load
Causes the controller’s RRM algorithms to consider 802.11 traffic from
Cisco lightweight access points in your wireless network when
assigning channels. For example, RRM can assign better reuse patterns
to access points that carry a heavier traffic load.
Options: Enabled or Disabled
Default: Disabled
Avoid Non-802.11a
(802.11b) Noise
Causes the controller’s RRM algorithms to consider noise (non-802.11
traffic) in the channel when assigning channels to lightweight access
points. For example, RRM may have access points avoid channels with
significant interference from non-access point sources, such as
microwave ovens.
Options: Enabled or Disabled
Default: Enabled
The following non-configurable RF channel parameter settings are also shown:
•
Signal Strength Contribution—This parameter is always enabled. RRM constantly monitors the
relative signal strength of all access points within the RF group to ensure near-optimal channel
reuse.
•
Channel Assignment Leader—The MAC address of the RF group leader, which is responsible for
channel assignment.
•
Last Channel Assignment—The last time RRM evaluated the current channel assignments.
•
DCA Sensitivity Level—The configured DCA sensitivity setting: low, medium, or high. This
setting determines how sensitive the DCA algorithm is to environmental changes, such as signal,
load, noise, and interference, when determining whether to change channels.
Note
See the config advanced {802.11a | 802.11b} channel dca sensitivity {low | medium |
high} CLI command in the “Using the CLI to Configure RRM” section on page 10-23 for
more information.
Note
To see why the DCA algorithm changed channels, click Monitor and then View All under
Most Recent Traps. The trap provides the MAC address of the radio that changed channels,
the previous channel and the new channel, the reason why the change occurred, the energy
before and after the change, the noise before and after the change, and the interference
before and after the change.
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Table 10-1
Parameter
RRM Parameters (continued)
Description
Tx Power Level Assignment Algorithm
Power Level Assignment The controller’s dynamic power assignment mode.
Method
Options: Automatic, On Demand, or Fixed
Default: Automatic
Power Level
Assignment
Method
Description
Automatic
Causes the controller to periodically evaluate and, if
necessary, update the transmit power for all joined access
points.
On Demand Causes the controller to periodically evaluate the
transmit power for all joined access points. However, the
controller updates the power, if necessary, only when you
click Invoke Power Update Now.
Note
Fixed
Prevents the controller from evaluating and, if necessary,
updating the transmit power for joined access points. The
power level is set to the fixed value chosen from the
drop-down box.
Note
Note
The controller does not evaluate and update the
transmit power immediately after you click
Invoke Power Update Now. It waits for the next
600-second interval. This value is not
configurable.
The transmit power level is assigned an integer
value instead of a value in mW or dBm. The
integer corresponds to a power level that varies
depending on the regulatory domain in which the
access points are deployed. See Step 4 on page
10-29 for information on available transmit
power levels.
For optimal performance, Cisco recommends that you use the
Automatic setting. Refer to the “Disabling Dynamic Channel
and Power Assignment Globally for a Controller” section on
page 10-31 for instructions if you ever need to disable the
controller’s dynamic settings.
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Table 10-1
RRM Parameters (continued)
Parameter
Description
The following non-configurable transmit power level parameter settings are also shown:
•
Power Threshold—The cutoff signal level used by RRM when determining whether to reduce an
access point’s power. The default value for this parameter is -70 dBm but can be changed through
the controller CLI on rare occasions when access points are transmitting at higher (or lower) than
desired power levels. See the “Using the CLI to Configure RRM” section on page 10-23 for the
CLI command.
•
Power Neighbor Count—The minimum number of neighbors an access point must have for the
transmit power control algorithm to run.
•
Power Update Contribution—The factors used for changing power assignment levels: load (L),
signal (S), noise (N), or interference (I).
•
Power Assignment Leader—The MAC address of the RF group leader, which is responsible for
power level assignment.
•
Last Power Level Assignment—The last time RRM evaluated the current transmit power level
assignments.
Coverage Hole Algorithm
Coverage (3 to 50 dB)
The maximum tolerable signal-to-noise ratio (SNR) level per client.
This value is used in the generation of traps for both the Coverage
Exception Level and Client Min Exception Level thresholds.
Default:12 dB (802.11b/g) or 16 dB (802.11a)
Client Min Exception Level
(1 to 75)
The minimum number of clients on an access point with a
signal-to-noise ratio (SNR) below the Coverage threshold. This
threshold works in conjunction with the Coverage and Coverage
Exception Level thresholds. A coverage exception is alerted if the
Coverage Exception Level percentage of clients (25%) and the Client
Min Exception Level number of clients (3) fall below the Coverage
threshold (12 dB). In this example, a coverage alarm would be
generated if at least 25% and a minimum of 3 clients have an SNR value
below 12 dB (802.11b/g) or 16 dB (802.11a).
Default:3
Profile Threshold for Traps—Profile thresholds are used principally for alarming and have no bearing
on the functionality of the RRM algorithms. When the values set for these threshold parameters are
exceeded, an SNMP trap (or an alert) is sent to WCS.
Interference (0 to 100%)
The percentage of interference (802.11 traffic from sources outside of
your wireless network) on a single access point.
Default: 10%
Clients (1 to 75)
The number of clients on a single access point.
Default: 12
Noise (–127 to 0 dBm)
The level of noise (non-802.11 traffic) on a single access point.
Default: –70 dBm
Utilization (0 to 100%)
The percentage of RF bandwidth being used by a single access point.
Default: 80%
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Table 10-1
RRM Parameters (continued)
Parameter
Coverage Exception
Level (0 to 100%)
Description
The percentage of clients on an access point that are experiencing a low
signal level but cannot roam to another access point. This value is based
on the Coverage threshold and the Client Min Exception Level
threshold.
Default: 25%
Noise/Interference/Rogue Monitoring Channels
Channel List
The set of channels that the access point uses for RRM scanning.
Options: All Channels, Country Channels, or DCA Channels
Default: Country Channels
Channel List Description
All
Channels
RRM channel scanning occurs on all channels supported
by the selected radio, which includes channels not
allowed in the country of operation.
Country
Channels
RRM channel scanning occurs only on the data channels
in the country of operation.
DCA
Channels
RRM channel scanning occurs only on the channel set
used by the dynamic channel allocation (DCA)
algorithm, which by default includes all of the
non-overlapping channels allowed in the country of
operation. However, you can specify the channel set to be
used by DCA if desired. To do so, follow the instructions
in Step 5.
Monitor Intervals
Noise Measurement
How frequently the access point measures noise and interference.
Range: 60 to 3600 seconds
Default: 180 seconds
Load Measurement
How frequently the access point collects information about the channel
load, which is then incorporated into the DCA algorithm.
Range: 60 to 3600 seconds
Default: 60 seconds
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Table 10-1
RRM Parameters (continued)
Parameter
Neighbor Packet
Frequency
Description
How frequently the access point measures signal strength and how
frequently neighbor packets (messages) are sent, which eventually
builds the neighbor list.
Range: 60 to 3600 seconds
Default: 60 seconds
Channel Scan Duration
The sum of the time between scans for each channel within a radio
band. The entire scanning process takes 50 ms per channel, per radio
and runs at the default Channel Scan Duration interval of 180 seconds.
The time spent listening on each channel is determined by the
non-configurable 50-ms scan time and the number of channels to be
scanned. For example, in the U.S. all 11 802.11b/g channels are
scanned for 50 ms each within the 180-second interval. So every 16
seconds, 50 ms is spent listening on each scanned channel (180/11 =
~16 seconds). The amount of time allocated for the entire scanning
process. The Channel Scan Duration parameter determines the interval
at which the scanning occurs.
Range: 60 to 3600 seconds
Default: 180 seconds
Step 3
Click Apply to commit your changes.
Step 4
Click Save Configuration to save your changes.
Step 5
If you want to specify the channels that the dynamic channel allocation (DCA) algorithm considers when
selecting the channels to be used for RRM scanning, follow these steps. This functionality is helpful
when you know that the clients do not support certain channels because they are legacy devices or they
have certain regulatory restrictions.
a.
Click Wireless > 802.11a or 802.11b/g > RRM > DCA to access the 802.11a (or 802.11b/g) > RRM
> DCA page (see Figure 10-6).
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Figure 10-6
802.11a > RRM > DCA Page
The DCA Channels field shows the channels that are currently selected.
b.
To select a channel, check its check box in the Select column. To exclude a channel, uncheck its
check box.
Range:
802.11a—20, 26, 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153,
157, 161, 165, 190, 196
802.11b/g—1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
Default:
802.11a—36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140, 149, 153, 157, 161
802.11b/g—1, 6, 11
Step 6
c.
Click Apply to commit your changes.
d.
Click Save Configuration to save your changes.
Repeat this procedure to set the same parameter values for every controller in the RF group.
Using the CLI to Configure RRM
Follow these steps to configure RRM using the CLI.
Step 1
Enter this command to disable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} disable
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Step 2
Perform one of the following:
•
To have RRM automatically configure all 802.11a or 802.11b/g channels based on availability and
interference, enter this command:
config {802.11a | 802.11b} channel global auto
•
To have RRM automatically reconfigure all 802.11a or 802.11b/g channels one time based on
availability and interference, enter this command:
config {802.11a | 802.11b} channel global once
•
To specify the channel set used for dynamic channel allocation (DCA), enter this command:
config advanced {802.11a | 802.11b} channel {add | delete} channel_number
You can enter only one channel number per command. This command is helpful when you know that
the clients do not support certain channels because they are legacy devices or they have certain
regulatory restrictions.
Step 3
Use these commands to configure the DCA algorithm parameters:
•
To control the DCA sensitivity with respect to changes in the environment, enter this command:
config advanced {802.11a | 802.11b} channel dca sensitivity {low | medium | high}
The DCA algorithm determines whether to make a channel change based on how much better a new
channel would be for the radio with the worst DCA metric in the radio band. The DCA metric is
comprised of noise, interference, channel load, and overlapping neighbors (other radios on the same
channel). This command allows you to control how sensitive the DCA algorithm is to environmental
changes, such as signal, load, noise, and interference, when determining whether to change
channels. Table 10-2 shows the three available DCA sensitivity levels.
Table 10-2
DCA Sensitivity Levels
DCA Sensitivity
Level
Description
2.4-GHz DCA Sensitivity
Threshold (dB)
5-GHz DCA Sensitivity
Threshold (dB)
High
High sensitivity to
environmental changes
5
5
Medium
(default)
Moderate sensitivity to
environmental changes
15
20
Low
Low sensitivity to environmental 30
changes
35
For example, if the radio with the worst DCA metric in the 2.4-GHz band has a metric of -60 dBm
on its current channel and the DCA algorithm finds that the metric would be -80 dBm on another
channel (which is an improvement of 20 dBm), the DCA algorithm would change the channel if the
DCA sensitivity is set to high or medium. It would not change the channel if the sensitivity is set to
low.
•
To define the time when DCA starts, enter this command:
config advanced {802.11a | 802.11b} channel dca anchor-time hour
where hour is an hour in the day from 0 to 23 (12:00 a.m. to 11:00 p.m.).
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•
To define how often DCA runs, enter this command:
config advanced {802.11a | 802.11b} channel dca interval value
where value is 0, 1, 2, 3, 4, 6, 8, 12, or 24. 0 = 10 minutes and is the default value. The rest of the
values represent hours. If you specify a value of 8, DCA would run every 8 hours.
For example, if you specify an anchor time of 0 and a DCA interval of 12, the DCA algorithm would
run at 12:00 a.m. and 12:00 p.m. every day.
Note
Step 4
When the controller reboots, the DCA algorithm runs every 10 minutes for the first 100
minutes, regardless of how the anchor-time and interval parameters are configured. This
initial startup phase enables the DCA algorithm to converge to a reliable channel before the
scheduled operation occurs. After the first 100 minutes, the DCA algorithm runs at only the
scheduled times.
Perform one of the following:
•
To have RRM automatically set the transmit power for all 802.11a or 802.11b/g radios at periodic
intervals, enter this command:
config {802.11a | 802.11b} txPower global auto
•
To have RRM automatically reset the transmit power for all 802.11a or 802.11b/g radios one time,
enter this command:
config {802.11a | 802.11b} txPower global once
•
To manually change the default transmit power setting of -70 dBm, enter this command:
config advanced {802.11a | 802.11b} tx-power-control-thresh threshold
where threshold is a value from -50 to -80 dBm. Increasing this value (between -50 and -65 dBm)
causes the access points to operate at higher transmit power rates. Decreasing the value has the
opposite effect.
In applications with a dense population of access points, it may be useful to decrease the threshold
to -75 or -80 dBm in order to reduce the number of BSSIDs (access points) and beacons seen by the
wireless clients. Some wireless clients may have difficulty processing a large number of BSSIDs or
a high beacon rate and may exhibit problematic behavior with the default threshold.
Note
Step 5
See the Power Threshold description in Table 10-1 for more information.
Enter this command to enable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} enable
Note
Step 6
To enable the 802.11g network, enter config 802.11b 11gSupport enable after the config
802.11b enable command.
Enter this command to save your settings:
save config
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Using the CLI to Debug RRM Issues
Use these commands to troubleshoot and verify RRM behavior:
debug airewave-director ?
where ? is one of the following:
•
all—Enables debugging for all RRM logs.
•
channel—Enables debugging for the DCA algorithm’s channel change. This command provides the
previous channel, the 802.11 interference energy (both the previous and current values in dBm), the
noise energy (both the previous and current values in dBm), and the reason why the channel was
changed. Possible reasons include:
– 0 = Other (could occur as a result of a manual channel change)
– 1 = Signal (could occur if the RSSI at which the neighbor access points are seen have changed
recently, possibly due to a channel change)
– 2 = Noise
– 4 = 802.11 interference
– 6 = Noise and 802.11 interference
•
detail—Enables debugging for RRM detail logs.
•
error—Enables debugging for RRM error logs.
•
group—Enables debugging for the RRM grouping protocol.
•
manager—Enables debugging for the RRM manager.
•
message—Enables debugging for RRM messages.
•
packet—Enables debugging for RRM packets.
•
power—Enables debugging for the RRM power assignment protocol.
•
profile—Enables debugging for RRM profile events.
•
radar—Enables debugging for the RRM radar detection/avoidance protocol.
•
rf-change—Enables debugging for RRM RF changes.
Overriding RRM
In some deployments, it is desirable to statically assign channel and transmit power settings to the access
points instead of relying on the RRM algorithms provided by Cisco. Typically, this is true in challenging
RF environments and non-standard deployments but not the more typical carpeted offices.
Note
If you choose to statically assign channels and power levels to your access points and/or to disable
dynamic channel and power assignment, you should still use automatic RF grouping to avoid spurious
rogue device events.
You can disable dynamic channel and power assignment globally for a controller, or you can leave
dynamic channel and power assignment enabled and statically configure specific access point radios
with a channel and power setting. Follow the instructions in one of the following sections:
•
Statically Assigning Channel and Transmit Power Settings to Access Point Radios, page 10-27
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•
Disabling Dynamic Channel and Power Assignment Globally for a Controller, page 10-31
Note
While you can specify a global default transmit power parameter for each network type that applies to
all the access point radios on a controller, you must set the channel for each access point radio when you
disable dynamic channel assignment. You may also want to set the transmit power for each access point
instead of leaving the global transmit power in effect.
Note
You can also override RRM using the Cisco Wireless Control System (WCS). Refer to the Cisco Wireless
Control System Configuration Guide for instructions.
Statically Assigning Channel and Transmit Power Settings to Access Point
Radios
This section provides instructions for statically assigning channel and power settings using the GUI or
CLI.
Note
Cisco recommends that you assign different nonoverlapping channels to access points that are within
close proximity to each other. The nonoverlapping channels in the U.S. are 36, 40, 44, 48, 52, 56, 60,
64, 149, 153, 157, and 161 in an 802.11a network and 1, 6, and 11 in an 802.11b/g network.
Note
Cisco recommends that you do not assign all access points that are within close proximity to each other
to the maximum power level.
Using the GUI to Statically Assign Channel and Transmit Power Settings
Follow these steps to statically assign channel and/or power settings on a per access point radio basis
using the GUI.
Step 1
Click Wireless > Access Points > Radios > 802.11a or 802.11b/g to access the 802.11a (or 802.11b/g)
Radios page (see Figure 10-7).
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Figure 10-7
802.11a Radios Page
This page shows all the 802.11a or 802.11b/g access point radios that are joined to the controller and
their current settings.
Step 2
Hover your cursor over the blue drop-down arrow for the access point for which you want to modify the
radio configuration and choose Configure. The 802.11a (or 802.11b/g) Cisco APs > Configure page
appears (see Figure 10-8).
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Figure 10-8
802.11a Cisco APs > Configure Page
Step 3
To assign an RF channel to the access point radio, choose Custom for the Assignment Method under RF
Channel Assignment and choose a channel from the drop-down box.
Step 4
To assign a transmit power level to the access point radio, choose Custom for the Assignment Method
under Tx Power Level Assignment and choose a transmit power level from the drop-down box.
The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer
corresponds to a power level that varies depending on the regulatory domain in which the access points
are deployed. The number of available power levels varies based on the access point model. However,
power level 1 is always the maximum power level allowed per country code setting, with each successive
power level representing 50% of the previous power level. For example, 1 = maximum power level in a
particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on.
Note
Refer to the hardware installation guide for your access point for the maximum transmit power
levels supported per regulatory domain. Also, refer to the data sheet for your access point for the
number of power levels supported.
Step 5
Click Apply to commit your changes.
Step 6
Click Save Configuration to save the changes to the access point radio.
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Step 7
Repeat this procedure for each access point radio for which you want to assign a static channel and power
level.
Using the CLI to Statically Assign Channel and Transmit Power Settings
Follow these steps to statically assign channel and/or power settings on a per access point radio basis
using the CLI.
Step 1
Enter this command to disable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} disable
Step 2
To specify the channel that a particular access point is to use, enter this command:
config {802.11a | 802.11b} channel Cisco_AP channel
Example: To configure 802.11a channel 36 as the default channel on AP1, enter this command:
config 802.11a channel AP1 36.
Step 3
To specify the transmit power level that a particular access point is to use, enter this command:
config {802.11a | 802.11b} txPower Cisco_AP power_level
Example: To set the transmit power for 802.11a AP1 to power level 2, enter this command:
config 802.11a txPower AP1 2.
The transmit power level is assigned an integer value instead of a value in mW or dBm. The integer
corresponds to a power level that varies depending on the regulatory domain in which the access points
are deployed. The number of available power levels varies based on the access point model. However,
power level 1 is always the maximum power level allowed per country code setting, with each successive
power level representing 50% of the previous power level. For example, 1 = maximum power level in a
particular regulatory domain, 2 = 50% power, 3 = 25% power, 4 = 12.5% power, and so on.
Note
Step 4
Refer to the hardware installation guide for your access point for the maximum transmit power
levels supported per regulatory domain. Also, refer to the data sheet for your access point for the
number of power levels supported.
Enter this command to save your settings:
save config
Step 5
Repeat Step 2 through Step 4 for each access point radio for which you want to assign a static channel
and power level.
Step 6
Enter this command to enable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} enable
Note
Step 7
To enable the 802.11g network, enter config 802.11b 11gSupport enable after the config
802.11b enable command.
Enter this command to save your settings:
save config
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Disabling Dynamic Channel and Power Assignment Globally for a Controller
This section provides instructions for disabling dynamic channel and power assignment using the GUI
or CLI.
Using the GUI to Disable Dynamic Channel and Power Assignment
Follow these steps to configure disable dynamic channel and power assignment using the GUI.
Step 1
Click Wireless > 802.11a or 802.11b/g > RRM > Auto RF to access the 802.11a (or 802.11b/g) Global
Parameters > Auto RF page (see Figure 10-2).
Step 2
To disable dynamic channel assignment, choose Off under RF Channel Assignment.
Step 3
To disable dynamic power assignment, choose Fixed under Tx Power Level Assignment and choose a
default transmit power level from the drop-down box.
Note
See Step 4 on page 10-29 for information on transmit power levels.
Step 4
Click Apply to commit your changes.
Step 5
Click Save Configuration to save your changes.
Step 6
If you are overriding the default channel and power settings on a per radio basis, assign static channel
and power settings to each of the access point radios that are joined to the controller.
Step 7
If desired, repeat this procedure for the network type you did not select (802.11a or 802.11b/g).
Using the CLI to Disable Dynamic Channel and Power Assignment
Follow these steps to disable RRM for all 802.11a or 802.11b/g radios.
Step 1
Enter this command to disable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} disable
Step 2
Enter this command to disable RRM for all 802.11a or 802.11b/g radios and set all channels to the
default value:
config {802.11a | 802.11b} channel global off
Step 3
Enter this command to enable the 802.11a or 802.11b/g network:
config {802.11a | 802.11b} enable
Note
Step 4
To enable the 802.11g network, enter config 802.11b 11gSupport enable after the config
802.11b enable command.
Enter this command to save your settings:
save config
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Viewing Additional RRM Settings Using the CLI
Use these commands to view additional 802.11a and 802.11b/g RRM settings:
•
show advanced 802.11a ?
•
show advanced 802.11b ?
where ? is one of the following:
ccx—Shows the Cisco Compatible Extensions (CCX) RRM configuration.
channel—Shows the channel assignment configuration and statistics.
logging—Shows the RF event and performance logging.
monitor—Shows the Cisco radio monitoring.
profile—Shows the access point performance profiles.
receiver—Shows the 802.11a or 802.11b/g receiver configuration and statistics.
summary—Shows the configuration and statistics of the 802.11a or 802.11b/g access points
txpower—Shows the transmit power assignment configuration and statistics.
Note
To troubleshoot RRM-related issues, refer to the Cisco Wireless LAN Controller Command Reference,
Release 3.2 for RRM (airewave-director) debug commands.
Configuring CCX Radio Management Features
You can configure two parameters that affect client location calculations:
•
Radio measurement requests
•
Location calibration
These parameters are supported in Cisco Client Extensions (CCX) v2 and higher and are designed to
enhance location accuracy and timeliness for participating CCX clients. See the “Configuring Cisco
Client Extensions” section on page 6-28 for more information on CCX.
For the location features to operate properly, the access points must be configured for normal, monitor,
or hybrid-REAP mode. However, for hybrid-REAP mode, the access point must be connected to the
controller.
Note
CCX is not supported on the AP1030.
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Radio Measurement Requests
When this feature is enabled, lightweight access points issue broadcast radio measurement request
messages to clients running CCXv2 or higher. The access points transmit these messages for every SSID
over each enabled radio interface at a configured interval. In the process of performing 802.11 radio
measurements, CCX clients send 802.11 broadcast probe requests on all the channels specified in the
measurement request. The Cisco Location Appliance uses the uplink measurements based on these
requests received at the access points to quickly and accurately calculate the client location. You do not
need to specify on which channels the clients are to measure. The controller, access point, and client
automatically determine which channels to use.
In controller software release 4.1, the radio measurement feature has been expanded to enable the
controller to also obtain information on the radio environment from the client’s perspective (rather than
from just that of the access point). In this case, the access points issue unicast radio measurement
requests to a particular CCXv4 client. The client then sends various measurement reports back to the
access point and onto the controller. These reports include information on the radio environment and data
used to interpret the location of the clients. To prevent the access points and controller from being
overwhelmed by radio measurement requests and reports, only two clients per access point and up to
twenty clients per controller are supported. You can view the status of radio measurement requests for a
particular access point or client as well as radio measurement reports for a particular client from the
controller CLI.
Controller software release 4.1 also improves the ability of the Location Appliance to accurately
interpret the location of a device through a new CCXv4 feature called location-based services. The
controller issues a path-loss request to a particular CCXv4 client. If the client chooses to respond, it
sends a path-loss measurement report to the controller. These reports contain the channel and transmit
power of the client.
Note
Non-CCX and CCXv1 clients simply ignore the CCX measurement requests and therefore do not
participate in the radio measurement activity.
Location Calibration
For CCX clients that need to be tracked more closely (for example, when a client calibration is
performed), the controller can be configured to command the access point to send unicast measurement
requests to these clients at a configured interval and whenever a CCX client roams to a new access point.
These unicast requests can be sent out more often to these specific CCX clients than the broadcast
measurement requests, which are sent to all clients. When location calibration is configured for
non-CCX and CCXv1 clients, the clients are forced to disassociate at a specified interval to generate
location measurements.
Using the GUI to Configure CCX Radio Management
Follow these steps to configure CCX radio management using the controller GUI.
Step 1
Click Wireless > 802.11a or 802.11b/g > Network. The 802.11a (or 802.11b/g) Global Parameters page
appears (see Figure 10-9).
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Figure 10-9
802.11a Global Parameters Page
Step 2
Under CCX Location Measurement, check the Mode check box to globally enable CCX radio
management. This parameter causes the access points connected to this controller to issue broadcast
radio measurement requests to clients running CCX v2 or higher. The default value is disabled (or
unchecked).
Step 3
If you checked the Mode check box in the previous step, enter a value in the Interval field to specify how
often the access points are to issue the broadcast radio measurement requests.
Range: 60 to 32400 seconds
Default: 60 seconds
Step 4
Click Apply to commit your changes.
Step 5
Click Save Configuration to save your settings.
Step 6
Follow the instructions in Step 2 of the “Using the CLI to Configure CCX Radio Management” section
below to enable access point customization.
Note
Step 7
To enable CCX radio management for a particular access point, you must enable access point
customization, which can be done only through the controller CLI.
If desired, repeat this procedure for the other radio band (802.11a or 802.11b/g).
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Using the CLI to Configure CCX Radio Management
Follow these steps to enable CCX radio management using the controller CLI.
Step 1
To globally enable CCX radio management, enter this command:
config advanced {802.11a | 802.11b} ccx location-meas global enable interval_seconds
The range for the interval_seconds parameter is 60 to 32400 seconds, and the default value is 60 seconds.
This command causes all access points connected to this controller in the 802.11a or 802.11b/g network
to issue broadcast radio measurement requests to clients running CCXv2 or higher.
Step 2
To enable access point customization, enter these commands:
•
config advanced {802.11a | 802.11b} ccx customize Cisco_AP {on | off}
This command enables or disables CCX radio management features for a particular access point in
the 802.11a or 802.11b/g network.
•
config advanced {802.11a | 802.11b} ccx location-meas ap Cisco_AP enable interval_seconds
The range for the interval_seconds parameter is 60 to 32400 seconds, and the default value is 60
seconds. This command causes a particular access point in the 802.11a or 802.11b/g network to
issue broadcast radio measurement requests to clients running CCXv2 or higher.
Step 3
To enable or disable location calibration for a particular client, enter this command:
config client location-calibration {enable | disable} client _mac interval_seconds
Note
Step 4
You can configure up to five clients per controller for location calibration.
To save your settings, enter this command:
save config
Using the CLI to Obtain CCX Radio Management Information
Use these commands to obtain information about CCX radio management on the controller.
1.
To see the CCX broadcast location measurement request configuration for all access points
connected to this controller in the 802.11a or 802.11b/g network, enter this command:
show advanced {802.11a | 802.11b} ccx global
2.
To see the CCX broadcast location measurement request configuration for a particular access point
in the 802.11a or 802.11b/g network, enter this command:
show advanced {802.11a | 802.11b} ccx ap Cisco_AP
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3.
To see the status of radio measurement requests for a particular access point, enter this command:
show ap ccx rm Cisco_AP status
Information similar to the following appears:
A Radio
Beacon Request.................................
Channel Load Request...........................
Frame Request..................................
Noise Histogram Request........................
Path Loss Request..............................
Interval.......................................
Iteration......................................
Enabled
Enabled
Disabled
Disabled
Disabled
60
5
B Radio
Beacon Request.................................
Channel Load Request...........................
Frame Request..................................
Noise Histogram Request........................
Path Loss Request..............................
Interval.......................................
Iteration................................... 5
4.
Disabled
Enabled
Disabled
Enabled
Disabled
60
To see the status of radio measurement requests for a particular client, enter this command:
show client ccx rm client_mac status
Information similar to the following appears:
Client Mac Address...............................
Beacon Request...................................
Channel Load Request.............................
Frame Request....................................
Noise Histogram Request..........................
Path Loss Request................................
Interval.........................................
Iteration........................................
5.
6.
00:40:96:ae:53:b4
Enabled
Disabled
Disabled
Disabled
Disabled
5
3
To see radio measurement reports for a particular client, enter these commands:
•
show client ccx rm client_mac report beacon—Shows the beacon report for the specified
client.
•
show client ccx rm client_mac report chan-load—Shows the channel-load report for the
specified client.
•
show client ccx rm client_mac report noise-hist—Shows the noise-histogram report for the
specified client.
•
show client ccx rm client_mac report frame—Shows the frame report for the specified client.
To see the clients configured for location calibration, enter this command:
show client location-calibration summary
7.
To see the RSSI reported for both antennas on each access point that heard the client, enter this
command:
show client detail client_mac
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Using the CLI to Debug CCX Radio Management Issues
Use these commands if you experience any CCX radio management problems.
1.
To debug CCX broadcast measurement request activity, enter this command:
debug airewave-director message {enable | disable}
2.
To debug client location calibration activity, enter this command:
debug ccxrm [all | error | warning | message | packet | detail {enable | disable}]
3.
The CCX radio measurement report packets are encapsulated in Internet Access Point Protocol
(IAPP) packets. Therefore, if the previous debug ccxrm command does not provide any debugs,
enter this command to provide debugs at the IAPP level:
debug iapp error {enable | disable}
4.
To debug the output for forwarded probes and their included RSSI for both antennas, enter this
command:
debug dot11 load-balancing
Configuring Pico Cell Mode
In large multi-cell high-density wireless networks, it can be challenging to populate a site with a large
number of access points to handle the desired cumulative bandwidth load while diminishing the
contention between access points and maintaining quality of service. To optimize RF channel capacity
and improve overall network performance, you can use the controller GUI or CLI to set high-density (or
pico cell) mode parameters.
These parameters enable you to apply the same receiver sensitivity threshold, clear channel assessment
(CCA) sensitivity threshold, and transmit power values across all access points registered to a given
controller. When a client that supports high density associates to an access point with high density
enabled, they exchange specific 802.11 information elements (IEs) that instruct the client to adhere to
the access point’s advertised receive sensitivity threshold, CCA sensitivity threshold, and transmit power
values. These three parameters reduce the effective cell size by adjusting the received signal strength
before an access point and client consider the channel accessible for the transfer of packets. When all
access points and clients raise the signal standard in this way throughout a high-density area, access
points can be deployed closer together without interfering with each other or being overwhelmed by
environmental and distant-rogue signals.
The benefits of a high-density-enabled wireless network include the following:
•
Most efficient use of the available spectrum
•
Significant increase in aggregate client throughput or throughput per square feet
•
Significant increase in wireless LAN capacity
•
Linear capacity growth
•
Higher interference tolerance by allowing WiFi to transmit over top of the interference
Figure 10-10 shows an example of a high-density network.
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Figure 10-10
High-Density Network Example
Guidelines for Using Pico Cell Mode
Follow these guidelines for using pico cell mode:
•
You can configure pico cell mode only for 802.11a networks.
•
High-density networking is supported on all Cisco lightweight access points (except the wireless
mesh access points) and on notebooks using the Intel PRO/Wireless 3945ABG and Intel Wireless
WiFi Link 4965AG clients.
•
To support high-density, both the clients and access points must be configured for high density. Do
not mix high-density and non-high-density devices in the same network.
•
High-density access points must be joined to a dedicated controller.
•
When you adjust the pico cell mode parameters, the following auto RF values automatically change:
– The default value of the Fixed option for the Power Level Assignment Method parameter (on
the 802.11a Global Parameters > Auto RF page) reflects the power setting that you specify for
the pico cell Transmit Power parameter.
– The default value of the Power Threshold parameter (on the Wireless > 802.11a > RRM > Auto
RF page) reflects the value that you specify for the pico cell CCA Sensitivity Threshold
parameter.
Using the GUI to Configure Pico Cell Mode
Follow these steps to configure pico cell mode using the controller GUI.
Step 1
Disable the 802.11a network before changing pico cell mode parameters. To do so, click Wireless >
802.11a > Network and uncheck the 802.11a Network Status check box.
Step 2
Click Wireless > 802.11a > Pico Cell to access the 802.11a > Pico Cell page (see Figure 10-11).
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Figure 10-11
Step 3
Step 4
802.11a > Pico Cell Page
Choose one of these options from the Pico Cell Mode drop-down box:
•
Disable—Disables pico cell mode. This is the default value.
•
V1—Enables pico cell mode version 1. This option is designed for use with legacy Airespace
products (those released prior to Cisco’s acquisition of Airespace). Cisco recommends that you
choose V2 if you want to enable pico cell mode.
•
V2—Enables pico cell mode version 2. Choose this option if you want to adjust the pico cell mode
parameters to optimize network performance in high-density areas, where all the clients support
high density.
If you chose V2 in Step 3, the 802.11a > Pico Cell page displays three configurable fields: Rx Sensitivity
Threshold, CCA Sensitivity Threshold, and Transmit Power (see Figure 10-12).
Figure 10-12
802.11a > Pico Cell Page with Pico Cell Mode V2 Parameters
Use the information in Table 10-3 to adjust the values of these parameters as necessary.
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Note
The default values for these parameters should be appropriate for most applications. Therefore,
Cisco recommends that you use the default values.
Table 10-3
Pico Cell Mode V2 Parameters
Parameter
Description
Rx Sensitivity Threshold
Specifies the current, minimum, and maximum values (in dBm) for
the receiver sensitivity of the 802.11a radio. The current value sets the
receiver sensitivity on the local radio. The min and max values are
used only for inclusion in the Inter-Access Point Protocol (IAPP)
high-density reports.
Default: -65 dBm (Current), -127 dBm (Min), and 127 dBm (Max)
CCA Sensitivity Threshold
Specifies the clear channel assessment (CCA) sensitivity threshold on
all radios in the high-density cell. The current value programs the
802.11a receiver. The min and max values are for advertisement in
IAPP reports.
Default: -65 dBm (Current), -127 dBm (Min), and 127 dBm (Max)
Transmit Power
Specifies the high-density transmit power used by both the access
point and client 802.11a radios.
Default: 10 dBm (Current), 0 dBm (Min), and 17 dBm (Max)
Note
The min and max values in Figure 10-12 and Table 10-3 are used only to indicate the range to
the client. They are not used on the access point.
Step 5
Click Apply to commit your changes.
Step 6
Re-enable the 802.11a network. To do so, click Wireless > 802.11a > Network and check the 802.11a
Network Status check box.
Step 7
Click Save Configuration to save your changes.
Note
If you change the values of the pico cell mode parameters and later want to reset them to their default
values, click Reset to Defaults and then click Apply.
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Using the CLI to Configure Pico Cell Mode
Note
Step 1
Refer to the “Using the GUI to Configure Pico Cell Mode” section on page 10-38 for descriptions and
default values of the parameters used in the CLI commands.
To disable the 802.11a network before changing pico cell mode parameters, enter this command:
config 802.11a disable
Step 2
Step 3
To enable pico cell mode, enter one of these commands:
•
config 802.11a picocell enable—Enables pico cell mode version 1. This command is designed for
use with a specific application. Cisco recommends that you use the config 802.11a picocell-V2
enable command if you want to enable pico cell mode.
•
config 802.11a picocell-V2 enable—Enables pico cell mode version 2. Use this command if you
want to adjust the pico cell mode parameters to optimize network performance in high-density areas.
If you enabled pico cell mode version 2 in Step 2, follow these steps to configure the receive sensitivity
threshold, CCA sensitivity threshold, and transmit power parameters:
a.
To configure the receive sensitivity threshold, enter this command:
config advanced 802.11a receiver pico-cell-V2 rx_sense_threshold min max current
b.
To configure the CCA sensitivity threshold, enter this command:
config advanced 802.11a receiver pico-cell-V2 cca_sense_threshold min max current
c.
To configure the transmit power, enter this command:
config advanced 802.11a receiver pico-cell-V2 sta_tx_pwr min max current
Step 4
If you enabled pico cell mode version 2 in Step 2 and you want to transmit a unicast IAPP high-density
frame request to a specific client, enter this command:
config advanced 802.11a receiver pico-cell-V2 send_iapp_req client_mac
Step 5
To re-enable the 802.11a network, enter this command:
config 802.11a enable
Step 6
To save your settings, enter this command:
save config
Using the CLI to Debug Pico Cell Mode Issues
Use these commands if you experience any pico cell mode problems.
1.
To see the current status of pico cell mode, enter this command:
show 802.11a
2.
To see the receiver parameters that are set by the pico cell mode commands, enter this command:
show advanced 802.11a receiver
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3.
To see the noise and interference information, coverage information, client signal-to-noise ratios,
and nearby access points, enter this command:
show ap auto-rf 802.11a Cisco_AP
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